Various types of clamps are employed to suspend and direct cables extending between supports and/or structures, such as between utility poles and/or between a utility pole and a building. One such type of clamp, commonly referred to as a drop wire clamp or drop cable clamp, is used to support and attach a cable to a building, pole, or support wire. The drop wire clamp supports the weight of the cable and maintains tension on the cable, while lessening or largely eliminating stress on the attachment points of the cable.
A currently employed type of drop wire clamp, also known as a wedge style compression-type drop wire clamp, includes an elongate shell or housing with a bottom and tapering sides, a mating slide assembly with a hanger loop, and a shim member disposed between the bottom of the housing and the slide assembly. The cable is held within the clamp between the bottom of the housing and the shim through compressive force or pressure applied by moving the slide assembly within the housing between the tapering sides. When the hanger loop of the slide assembly is attached to a pole, it exerts a pulling force on the slide assembly within the housing which causes a compressive force to be exerted on the cable disposed between the shim and the housing bottom. Examples of such wedge style compression-type drop wire clamps are known from U.S. Pat. No. 6,581,251 (Malin); U.S. Pat. No. 6,732,981 (Franks et al.); and U.S. Pat. No. 7,234,669 (Franks, Jr.).
Cable manufacturers go to great pains to produce cable with an outer jacket that is as nearly perfectly smooth and blemish free as is possible, and various factors, such as mechanical and thermal effects, allow the cable with its smooth outer jacket to move and slip within such wedge style installation clamps. The smoother the cable jacket, the greater the clamping pressure needed to reduce the degree of cable slippage in typical wedge style installation clamps. In turn, the greater the clamping pressure, the more likely it is that certain types of cables, such as fiber optic-based cables, will be damaged by the clamping pressure exerted on the cable.
In the past, the issue of cable slippage in wedge style installation clamps has been addressed exclusively from the clamp side with a variety of clamping designs in an attempt to achieve a tight clamping environment for the smooth surface cable. Thus, different styles of wedge clamps and clamp plates have been introduced to reduce the cable slippage, and it has been suggested, e.g., to include a plurality of ribs, holes, or a grate-like surface in a compression portion of the clamp, or to add an abrasive coating, such as an enamel and crushed glass mixture, to the clamping portion of the clamp. An example of such an attempt to address the issue of cable slippage exclusively from the clamp side is the drop wire clamp proposed in U.S. Pat. No. 7,367,534 (Franks, Jr.). However, slippage of the type of smooth-surfaced cable currently produced occurs even in such wedge type drop wire clamps with ribs, holes, grate-like surfaces or abrasive coatings.
It has also been suggested that ice loading of aerial cable might be reduced or that wind performance might be improved by providing a spiral shape to the rounded surface of the outer jacket of cable having a generally rounded cross section, but such a spiral configuration does not provide a significant increase in the friction properties of the cable jacket. Indeed, the presumed improvement in wind performance suggests a reduction in the friction properties of the cable jacket.
Field related installation issues of movement and slippage of cable within wedge style installation clamps remain common with drop cables.